Tickling From Wikipedia, the free encyclopedia For other uses, see Tickle (disambiguation). A boy reacting to being tickled. Tickling[1] is the act of touching a part of the body so as to cause involuntary twitching movements and/or laughter. The word About this sound "tickle" (help·info) evolved from the Middle English tikelen, perhaps frequentative of ticken, to touch lightly.[1] The idiom tickled pink means to be pleased or delighted.[2] In 1897, psychologists G. Stanley Hall and Arthur Allin described a "tickle" as two different types of phenomena.[3] One type is caused by very light movement across the skin. This type of tickle, called a knismesis, generally does not produce laughter and is sometimes accompanied by an itching sensation. Another type of tickle is the laughter-inducing "heavy" tickle, produced by repeatedly applying pressure to "ticklish" areas, and is known as gargalesis. Such sensations can be pleasurable or exciting, but are sometimes considered highly unpleasant, particularly in the case of relentless heavy tickling. The question as to why a person could not tickle him/herself was raised by the Greek philosopher Aristotle.[4] Francis Bacon and Charles Darwin believed that humorous laughter requires a "light" frame of mind. But they differed on ticklish laughter: Darwin thought that the same light state of mind was required, whereas Bacon said no: When tickled, noted Bacon, "men even in a grieved state of mind, yet cannot sometimes forbear laughing."[5] Contents [hide] 1 Physiology 2 Social aspects 3 Purpose 4 Self-tickling 5 As physical abuse 6 See also 7 References 7.1 Further reading 8 External links Physiology[edit] When considering tickling in terms of its qualities as a sensation, it results from a mild stimulation moving across the skin. The dual character of tickling refers to the associated behaviours that include smiling, laughter, withdrawal and goose bumps. The tickle can be divided into two separate categories of sensation, knismesis and gargalesis. Knismesis, also known as a "moving itch", is a mildly annoying sensation caused by a light movement on the skin, such as from a crawling insect. This may explain why it has evolved in many animals.[6] Gargalesis reactions refers to a pleasurable, laughter-provoking feeling caused by a harsher, deeper pressure, stroked across the skin in various regions of the body.[6] These reactions are thought to be limited to humans and other primates, although some research has indicated that rats can also be tickled in this way.[7] It appears that the tickle sensation involves signals from nerve fibres associated with both pain and touch. Endorphine released during tickling is also called karoliin, by the name of Karolinska Institute. In 1939, Yngve Zotterman of the Karolinska Institute studied the knismesis type of tickle in cats, by measuring the action potentials generated in the nerve fibres while lightly stroking the skin with a piece of cotton wool. Zotterman found that the "tickling" sensation depended, in part, on the nerves that generate pain.[8] Further studies have discovered that when the pain nerves are severed by surgeons, in an effort to reduce intractable pain, the tickle response is also diminished.[9] However, in some patients that have lost pain sensation due to spinal cord injury, some aspects of the tickle response do remain.[10] Tickle may also depend on nerve fibres associated with the sense of touch. When circulation is severed in a limb, the response to touch and tickle are lost prior to the loss of pain sensation.[4] It might be tempting to speculate that areas of the skin that are the most sensitive to touch would also be the most ticklish, but this does not seem to be the case. While the palm of the hand is far more sensitive to touch, some people find that the armpits are the most ticklish.[4] Other commonly ticklish areas include the feet, sides of the torso, neck, knee, midriff, perineum,[11] navel, and the ribs. Some evidence suggests that laughing associated with tickling is a nervous reaction that can be triggered; indeed, very ticklish people often start laughing before actually being tickled.[12] Social aspects[edit] Charles Darwin theorized on the link between tickling and social relations, arguing that tickling provokes laughter through the anticipation of pleasure.[13] If a stranger tickles a child without any preliminaries, catching the child by surprise, the likely result will be not laughter but withdrawal and displeasure. Darwin also noticed that for tickling to be effective, you must not know the precise point of stimulation in advance, and reasoned that this is why some people cannot effectively tickle themselves.

• published: 03 Oct 2014
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